His saying: "Kaf-Ha-Ya-'Ayn-Sad" (كهيعص). Al-Hasan used to say: "I do not know its interpretation, except that a group of the Companions of the Prophet, peace be upon him, used to say: 'They are the names of the Surahs and their opening letters (fawatih).'"
قَوْله: ﴿كهيعص﴾ كَانَ الْحَسَنُ يَقُولُ: لَا أَدْرِي مَا تَفْسِيرُهُ، غَيْرَ أَنَّ قَوْمًا مِنْ أَصْحَابِ النَّبِيِّ عليه السلام كَانُوا يَقُولُونَ: أَسْمَاءُ السُّوَرِ وَفَوَاتِحُهَا.